Abstract: At approximately 8:30 a.m. on March 7, 1991, Employee #1 was looking over some equipment that was to be removed from a maintenance operation involving the replacement of a header in an operating oil field. He began experiencing symptoms of exposure to hydrogen sulfide and attempted to escape, at the same time warning Employees #2 through #5 and four other coworkers who were in the area. He was able to get away from the gas cloud, but almost passed out upon reaching safety. He was hospitalized, along with Employees #2 through #5, who also complained of exposure to the gas. The previous day's high temperature had heated up the line, releasing hydrogen sulfide from the metal or residues. The gas, which is heavier than air, leaked out of a partially open needle valve and pooled in the depressions in the surrounding area. When Employee #1 walked into the pooled hydrogen sulfide, it rose into his face.